Abstract
Neurons in the superior colliculus (SC) integrate cross-modal inputs to generate responses that are more robust than to either input alone, and are frequently greater than their sum (superadditive enhancement). Previously, the principles of a real-time multisensory transform were identified and used to accurately predict a neuron's responses to combinations of brief flashes and noise bursts. However, environmental stimuli frequently have more complex temporal structures that elicit very different response dynamics than previously examined. The present study tested whether such stimuli (i.e., pulsed) would be treated similarly by the multisensory transform. Pulsing visual and auditory stimuli elicited responses composed of higher discharge rates that had multiple peaks temporally aligned to the stimulus pulses. Combinations pulsed cues elicited multiple peaks of superadditive enhancement within the response window. Measured over the entire response, this resulted in larger enhancements than expected given enhancements elicited by non-pulsed (“sustained”) stimuli. However, as with sustained stimuli, the dynamics of multisensory responses to pulsed stimuli were highly related to the temporal dynamics of the unisensory inputs. This suggests that the specific characteristics of the multisensory transform are not determined by the external features of the cross-modal stimulus configuration; rather the temporal structure and alignment of the unisensory inputs is the dominant driving factor in the magnitudes of the multisensory product.
Highlights
Brains integrate information across their multiple sensory systems to enhance the detection, localization, and identification of external stimuli, improving perceptual and behavioral responses to them
auditory bursts (As) predicted by Miller et al (2017), the temporal dynamics of the multisensory responses were well-linked to these unisensory temporal dynamics
Multisensory responses were consistent with a principle of real time integration; that is, converging visual and auditory inputs appeared to be integrated as soon as they arrived at the target neuron without delay or wind-up (Miller et al, 2017)
Summary
Brains integrate information across their multiple sensory systems to enhance the detection, localization, and identification of external stimuli, improving perceptual and behavioral responses to them (see reviews in Stein, 2012). Within the SC, afferents relaying independent signals from multiple sensory regions (visual, auditory, and somatosensory) converge onto target multisensory neurons that transform their inputs to integrated multisensory responses When these signals relay spatiotemporally concordant cross-modal cues, SC multisensory. Since the principles of this transform place such great importance on the temporal dynamics of the unisensory inputs, we sought to evaluate whether these principles would hold for SC responses to cues with a more complex temporal structure. This was the goal of the present effort
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